This invention relates to electric generator and motor structures and more particularly to an improved four pole wave wound direct current rotary machine having plural turn open windings on an armature.
For four pole wave wound direct current motors operated at relatively low speeds and/or relatively high voltages, there is a tendency for excessive currents to flow in armature windings having only a single turn. One common method for limiting the currents in the armature windings is to form the windings with a plurality of turns. An armature of this type for a D.C. motor is illustrated, for example, in U.S. Pat. No. 3,506,864 which is directed to winding an armature with a plurality of turns extending between two spaced slots in a laminated core. However, armatures of this type are only practical with thin flexible wire having a round cross section. It is often desirable to wind the armature with wire having a square or rectangular cross section. Such a wire cross section increases the efficiency of the armature by completely filling the space within each armature slot, as distinguished from having perhaps 25% or more air space in each armature slot when round wires are used. Heretofore, when heavy gauge wires and rectangular cross section wires were used for winding armatures, it was necessary either to limit each winding to a single turn in order to place the conductor in the armature slot or to form each winding from a plurality of sections which are welded or soldered together to form a continuous conductor. This greatly increases the complexity and cost of manufacturing the armature.
The prior art has also suggested that the number of armature windings may be increased, for example, by doubling the number of windings in each armature core slot. One winding is connected between two commutator segments spaced substantially 180.degree. apart and a second winding in the same core slot is connected between the adjacent two commutator segments, also spaced substantially 180.degree. apart. However, this arrangement requires twice as many commutator segments than in a conventional armature having only single turn windings. The prior art also has suggested that a double winding may be applied to the armature in four slots mechanically spaced 90.degree. apart about the armature. However, the prior art has indicated that such an arrangement is not applicable to four pole machines, since the winding ends must be connected to commutator segments spaced 360.degree. apart. See the treatise by A. S. Langsdorf, "Principles of Direct-Current Machines", Fifth Edition, published in 1940 by McGraw Hill Book Company (New York and London), pages 317-365, especially pages 348 and 349, or the Sixth Edition, published in 1959, pages 45 to 90, especially pages 64 and 65.